The following patents disclose various types of self-injecting syringes: U.S. Pat. No. 98,478, granted Jan. 4, 1870, to Charles H. Eccleston; U.S. Pat. No. 922,331, granted May 1, 1909, to Thomas M. Quarles; U.S. Pat. No. 1,845,036, granted Feb. 16, 1932, to Herbert H. Busher; U.S. Pat. No. 1,921,034, granted Aug. 8, 1933, to Norman O. La Marche; U.S. Pat. No. 2,664,086, granted Dec. 29, 1953, to Gerald O. Transue and U.S. Pat. No. 3,605,743, granted Sept. 20, 1971, to Raul O. Arce; and U.S. Pat. No. 4,407,283, granted Oct. 4, 1983 to Francis D. Reynolds.
U.S. Pat. No. 3,224,445, granted Dec. 21, 1965, to Norman W. Melott and U.S. Pat. No. 3,583,399, granted June 8, 1971, to Anthony F. Ritsky, both disclose syringes which are adapted for performing the procedure known as "aspiration". The procedure known as "aspiration" is defined in these patenets.
Additional aspirating syringes, requiring cartridges of a special construction, are disclosed by the following U.S. Pat. Nos.: 2,554,744, granted May 29, 1951, to Niels B. Jorgensen; 2,693,184, granted Nov. 2, 1954, to Marshall L. Lockhart; 2,693,185, granted Nov. 2, 1954, to Marshall L. Lockhart; 3,045,674, granted July 24, 1962, to Samuel D. Goldberg; 3,340,872, granted Sept. 12, 1967, to Thomas S. Cox; 3,618,603, granted Nov. 9, 1971, to Myron F. Levenson; 3,766,918, granted Oct. 23, 1973, to John D. Kessel and 4,381,779, granted May 3, 1983, to Herman Margulies.
The device shown by the aforementioned U.S. Pat. No. 3,224,445 includes a plunger having an arrow-shaped barb at its forward end which enters into the piston of a cartridge. The theory of the shape is that the barb will become connected to the piston. Its purpose is to connect together the plunger and the piston so that when a plunger is pulled rearwardly, the piston will move rearwardly with it. The barb 42 is not constructed to in any way cause the forward portion of the piston to become distorted, for providing automatic aspiration when pressure is removed from the plunger. In practice it has been found that the barb does not effectively grip the piston.
The various patents introduced above speak for themselves and therefore do not need to be specifically described in any detail. However, such patents, and the various patents cited against them, should be carefully considered for the purpose of putting the present invention into proper perspective relative to the prior art.